1. Field of the Invention
The present invention relates to a semiconductor manufacturing apparatus,and more specifically it relates to a part-exchanging mechanism in an apparatus which processes a semiconductor wafer within a hermetically sealed space.
2. Description of the Related Art
In the past, many methods and apparatuses have been known as methods of manufacturing semiconductors by processing a semiconductor wafer in a hermetically sealed space in accordance with a prescribed method.
Known methods include performing, for example, epitaxial growth with respect to a semiconductor wafer, the method of performing vapor deposition onto a semiconductor wafer, and the method of performing dry etching or plasma CVD processing of a semiconductor wafer.
In performing any of theses types of processing on a semiconductor wafer, because the prescribed processing is performed in a hermetically sealed space, in addition to it being necessary to transport the semiconductor wafer into the above-noted hermetically sealed processing space and to transport a semiconductor wafer which has been processed out from the hermetically sealed processing space, supporting components provided inside the hermetically sealed processing space and which hold or support the semiconductor wafer which is being processed, and processing components such as electrodes or shower plates and the like provided in this space for the purpose of performing the prescribed processing on the above-noted semiconductor wafer can deteriorate during this processing, accumulate impurities or be otherwise contaminated, so that they do not function in the manner that they should, this resulting in the need to replace either the supporting components or the processing components or both each time a prescribed amount of processing time has elapsed.
However, because the above-noted processing of the semiconductor wafer is carried out in a hermetically sealed processing space, it is necessary to perform these exchanging operations in a manner that does not disturb the hermetically sealed condition, this not only requiring a complex mechanism, but also a complex exchanging operation.
For example, taking the example of a semiconductor manufacturing apparatus which processes a semiconductor wafer using the plasma CVD processing method, the above-noted problem can be described specifically as follows.
Specifically, when performing plasma CVD processing of a semiconductor wafer, a widely used method is to form an insulating film on the semiconductor wafer by performing plasma CVD processing using a gas such as TEOS, SiH4, O2 or the like.
A chamber which is used in plasma CVD processing can be of the single-wafer type or the batch type, and because of the difficult of controlling the process parameters for each individual semiconductor wafer in a batch-type chamber, with semiconductor wafer sizes growing in the future, it is thought that the single-wafer type will become the main type used.
FIG. 11 is a cross-sectional view which shows an example of a conventional single-wafer type plasma CVD apparatus. As shown in FIG. 11, this single-wafer plasma CVD apparatus is formed from a process chamber 37, which has a process chamber body 4 and process chamber cover 5, and a wafer transport chamber 32, the above-noted process chamber 37 and transport chamber 32 being separated by a gate valve 9.
Inside the wafer transport chamber 32, which is hermetically sealed by the wafer transport chamber outer wall 7, a wafer transport robot 13, is driven by a wafer transport robot drive section 15, is provided, and inside the process chamber 37, a wafer-heating heater block 16, with a built-in heater, wafer position adjusting up/down elevator pins 21, a susceptor 1, and a shower head 2 are provided, the susceptor 1 and shower head 2 being held at the prescribed position by bolts 35.
The operation of the above-noted apparatus described as follows.
The semiconductor wafer 3 is rested on a fork 11 of the wafer transport robot 13, and a vacuum is generated in the wafer transport 32 via the wafer transport chamber exhaust port 28. After the wafer transport chamber 32 reaches the same pressure as the process chamber 37, in which a vacuum is generated via the process chamber exhaust port 26, the gate valve 9 is opened. The fork 11 of the wafer transport robot 13 extends in the direction of the process chamber 37, and the semiconductor wafer 3 is transported to inside the process chamber 37.
When this is done, the up/down elevator pin drive section 23 causes the wafer position adjusting up/down elevator pins 21 to slide upward, the wafer transport robot 13 rests the semiconductor wafer 3 onto the pins, and then returns into the wafer transport chamber 32. Then, the gate valve 9 closes, the wafer position adjusting up/down elevator pins 21 slide downward, and the semiconductor wafer 3 is rested onto the susceptor 1. Next, process gas is led into the process chamber 37 via a large number of holes in the shower head 2 from the gas inlet 29, and a high-frequency output voltage is applied between the susceptor 1 and the shower head 2, thereby forming an insulation film on the semiconductor wafer 3. After the growth is completed, the semiconductor wafer 3 is transported out of the process chamber 37 in a sequence that is the reverse of the one followed when it was transported thereinto.
In addition, after feeding cleaning gas by passing it through many holes in the shower head 2, a high-frequency output voltage is applied between the susceptor 1 and the shower head 2, to remove the film that grew inside the process chamber 37.
In a conventional single-wafer type CVD apparatus as described above, the exchange of a deteriorated susceptor and shower head are performed by returning the process chamber to atmospheric pressure and lowering the temperature of the heater block, after which the chamber cover 5 is opened, and the bolts 35 which hold the susceptor 1 and shower head 2 are removed. However, this operation exposes the inner walls of the process chamber to the oxygen and moisture components contained in the air. The oxygen and moisture components react with residual gas that has become adsorbed into the inner walls of the process chamber. Additionally, the oxygen and moisture components themselves are adsorbed into the inner walls of the process chamber.
Furthermore, by reducing the temperature of the heater 16, the inside of the process chamber is exposed to a large temperature change, resulting in a flaking of material which has formed on the inner walls of the process chamber due to a difference in thermal shrinkage rate. These phenomena cause the generation of particles and a change in film properties. At present, the inside walls of the chamber are wiped with ethanol as a countermeasure, but not only is this task very troublesome, but also there is the problem of not being able to completely remove generated particles or oxygen and moisture components which have become attached to the inner walls of the chamber.
In the CVD method as applied to chemical semiconductors such as GaAs, there is a method, as disclosed in Japanese Unexamined Patent Publication H4-360523, a chamber in which a susceptor is mounted is provide at the bottom part of the process chamber, the susceptor and the bottom surface of the chamber, known as a skirt, being exchanged in a vacuum. However, the application of this method to a single-wafer type CVD apparatus causes the construction of the bottom part of the susceptor to become complex, and also causes the problem of lack of space to provide a chamber into which the susceptor is mounted. Even if space can be obtained for providing the chamber into which the susceptor is mounted, a problem to be described below prevents exchange in a clean condition.
In the conventional single-wafer plasma CVD apparatus, once when the susceptor was exchanged, surface temperature of the susceptor is necessarily varied, even when it is controlled so that the temperature of the heater block after the exchange operation was carried out, is set at temperature identical to that before the exchange operation was carried out.
This fact is based upon a phenomena in that an amount of thermal transmission from the heater block to the susceptor, will be changed due to a variation in an area of contacting phase formed between the susceptor made of aluminum and the heater block made of aluminum.
The susceptor and heater contact surface area is influenced by non-uniformities in the bottom surface of the susceptor and the contact load between the susceptor and the heater. Because of the non-uniformity in the bottom surface of the susceptor, which differs for each susceptor, to limit the surface temperature variation of the susceptor, it is necessary to cause the susceptor to make pressurized contact with the heater block with a fixed force. However, in the past, because the method of doing this, as shown in FIG. 11, was by means of the bolt tightening from the inside, it was not possible to cause a pressurized contact in a vacuum condition. That is, from the technology in the Unexamined Patent Application Publication H4-360523, because it is only possible to transport the susceptor to the process chamber in a vacuum, heretofore it was not possible either remove the susceptor which was held by a tightened bolt or to achieve a pressurized contact of the susceptor on the top of the heater block. Also, because the shower head which was mounted to the bottom surface of cover was also held by a bolt from the inside, it was not possible to apply the above-noted technology, of the past, in which only transport is done in a vacuum, to a single-wafer type plasma CVD apparatus. That is, even if the above-noted technology of the past were to be applied to a single-wafer type plasma CVD apparatus, after transporting the susceptor or the shower head in a vacuum, because it is necessary to return to atmospheric pressure to perform the required mounting, the result is that the above-noted problems of residual gases with regard to oxygen and moisture components, and with regard to flaking of material which has formed on the inner walls of the chamber are not solved.